Food Safety Focus (84th Issue, July 2013) – Food Incident Highlight

Heavy Metals in Lime-preserved Eggs

Last month, the media reported that industrial copper sulphate, which might contain heavy metals as contaminants, was being used as an additive to speed up production of lime-preserved eggs (also known as "thousand-year eggs") in Mainland China. The incident has raised public concerns.

Copper is an essential micronutrient. In the Mainland, copper sulphate is a permitted processing aid that can be used to substitute lead oxide in the production of lime-preserved eggs in order to reduce the level of lead present in the final products. Excessive chronic exposure to lead can cause damages to kidneys and the central nervous system.

In Hong Kong, all poultry eggs, including lime-preserved eggs, imported from the Mainland must be sourced from registered farms and processing plants, and accompanied with health certificates. Results of recent surveillance conducted by the Centre for Food Safety on heavy metals, including lead, in lime-preserved eggs were all satisfactory. Food manufacturers should only use those food additives that are approved for use in food. Members of the public are reminded to obtain food from reliable sources.